1. Field of the Invention
The present invention relates to a battery module. More particularly, the present invention relates to a battery module having an improved structure for electrically connecting a plurality of unit cells.
2. Description of the Related Art
A secondary (rechargeable) battery can be repeatedly charged and discharged unlike a primary battery.
A low-capacity rechargeable battery typically includes one unit cell and can be used for a portable small electronic device such as a mobile phone, a laptop computer and the like. On the other hand, a large-capacity rechargeable battery typically includes a plurality of unit cells and can be used as a power source for driving a motor for a hybrid electric automobile and the like.
The rechargeable battery can be fabricated in various shapes, for example, as a cylinder or a prism.
Multiple rechargeable batteries may be connected in series and thereby form a battery module with large capacity, so that the battery module can be used for driving a motor for an electric vehicle and the like.
As such, the large capacity battery module is composed of a plurality of a individual rechargeable batteries (unit cells).
A unit cell includes an electrode assembly having positive and negative electrodes and a separator interposed therebetween. A case houses the electrode assembly and a cap assembly is combined with the case and seals it.
When the unit cell is formed as a prismatic shape, the cap assembly can be mounted with positive and negative terminals, which protrude out of the cap assembly and are electrically connected with the positive and negative electrodes.
Multiple unit cells are arranged at a predetermined interval and may be connected in a series or in a parallel to form a battery module.
In general, unit cells in a battery module are electrically connected through individual conductors which are connected to positive and negative terminals of the unit cells.
The conductor is typically fixed with the positive and negative terminals by welding or by using a separate member, such as a nut.
However, since a battery module includes many unit cells, it becomes inconvenient to respectively connect all the unit cells using separate conductors.
Particularly, when the conductors are fixed with a nut, each conductor is respectively fastened with a nut. Such assembly can be burdensome and time consuming.
In addition, when some of the unit cells in a battery module have so many nuts that need to be unfastened to replace a troublesome cell, significant time and effort may be needed to maintain the battery module.
Furthermore, when the conductors are fixed by welding, it becomes difficult to replace a troublesome unit cell in a battery module.
This problem can be particularly troublesome for a high power automobile battery module such as those used by an electric vehicle or a hybrid electric automobile.